1. Field of the Invention
The present invention relates to method of fabricating TiO2/CNT photocatalysts and a photocatalytic filter provided by the same and, more particularly, to a method of fabricating visible light absorbed TiO2/CNT photocatalysts and a photocatalytic filter provided by the same.
2. Description of Related Art
A photocatalyst is a material that can provide various functions such as sterilization, deodorization, and cleaning by the free radicals thereof being generated after exposure to light. Many materials have been taken as the photocatalyst material, and among them titanium dioxide is the mostly used one. In the prior arts, a titanium dioxide film is usually formed by using a sol-gel method, but the provided photocatalyst titanium dioxide film can work (be able to generate free radicals) only under the exposure to UV lights. Therefore, if a conventional photocatalyst titanium dioxide film is illuminated with visible light (with wavelength of longer than 400 nm), free radicals cannot be generated since only with the exposure to UV lights can the conventional photocatalyst be excited to an excited state. Accordingly, when a conventional photocatalyst titanium dioxide film is used to provide functions such as sterilization, deodorization, and cleaning, an artificial UV light source should be provided to illuminate the photocatalyst otherwise the photocatalyst can be used only at an outdoor site, i.e., with naturally-occurring UV.
US 2005/0239644 disclosed a method of fabricating photocatalysts, in which an active sol-gel is coated on a substrate to provide a titanium dioxide film. The precursor used therein comprises n-butyl titanate, ethane, diethanolamine, and water. However, the photocatalysts titanium dioxide film provided thereof still cannot operate without the illumination of UV lights, whereby the application of the photocatalysts is quite limited to the environment having naturally-occurring UV light or should be assisted with an artificial UV light source.
Reference with FIG. 1, a conventional photocatalyst filter is shown, which is made by dipping a cloth such as a polyethylene fiber cloth in a titanium dioxide solution to form a titanium dioxide layer 12 on the cloth fiber 11, and subsequently followed with a drying process. However, the surface area of the formed titanium dioxide layer is small due to the small surface area of the fiber cloth, which results in a small active surface of the photocatalyst filter. Also, some titanium dioxide molecules may aggregate and form agglomeration (granules) thus reducing the uniformity of titanium dioxide layer and resulting in a negative influence to the photodegradation efficiency of the photocatalyst.
Therefore, it is desirable to provide an improved photocatalyst filter and a method of providing the same to obviate the aforementioned problems and enable the photocatalyst filter to be usable (operable) under the exposure of visible light and UV light.